Senator Lamar Alexander calls the mercury problem at Y-12 one of the biggest issues from the Cold War era.

"Reduce the amount of mercury that comes as the department over a long period of time tears down the buildings where they used mercury in the process to make nuclear weapons. That disturbs the mercury and creates more that might go into the water," he said.

To do that, he details plans for a water treatment facility at the start of the East Fork Poplar Creek. Mercury usually impacts people if they eat fish laced with that toxin. It can cause severe damage to the brain and nervous system.

Senator Alexander says as clean-up efforts wrap up at sites like K-25, that will free up the federal government to focus on the mercury threat on the grounds of Y-12.

The project has an expected price tag of $120 million. Designs are in the works, and construction is expected to start in 2017. The plant would open in 2019.